Crane boom suspension



Sept. 9, 1952 K. EQGRUNDVIG CRANE BOOM SUSPENSION Filed Dec. 15, 1947 wide XNVENTOE, 7

ATTORNEY.

Patented Sept. 9, 1952 CRANE BOOM SUSPENSION Knut E. Grundvig, Chicago, Ill., assignor to Bucyrus-Erie Company, South Milwaukee, Wis., a corporation of Delaware Application December 15, 1947; Serial No. 791,845

My invention relates to new and useful improvements insuspension for crane booms, more particularly for the very long booms on that type of crane known as draglineexcavators.

In such machines it is important'that the boom and its suspension means be as light as possible. In the past, in the case of a long slender inclined boom suspended by guys extending from an A-frame on the base of the machine to the outer point of the boom, it has been customary to interpose between the A-frame and boom a strut or mast pivoted to the front of the base adjacent the foot of the boom and extending forwardly diagonally upward at a steeper inclination than the boom. This mast has two functions: (1) it supports the boom guys above the line between the A-frame and boom point, thus imparting an increased upward component on the boom in all operating positions of the boom, and (2) it permits the use of fixed-length guys between the mast and the boom, these guys providing permanent fixed supports from which to hang intermediate suspenders for the boom. This type of construction is shown and described more fully in U. S. Patent No. 2,378,915, issued June 26, 1945, to Trevor 0. Davidson.

A diiliculty withsuch a boom suspension is that the mast increases the weight of the machine, and increases the moment of momentum which resists the starting and stopping of the swing of the machine.

Accordingly it is the principal object of my invention to devise a boom suspension that will provide the advantages of the mast-type suspension without substantially increasing the weight or the moment of momentum.

In addition to my principal object, above stated, I have worked out a number of novel and useful details, which will be readily evident as the description progresses.

My invention consists in the novel parts and in the combination and arrangement thereof, which are defined in the appended claims, and of which one embodiment is exemplified in the accompanying drawings, which are hereinafter particularly described and explained.

Throughout the description the same reference number is applied to the same member or to similar members.

. Figure l is a plan view, somewhat conventionalized, of my boom suspension.

Figure 2 is a side elevation, taken along the lines 2-2 of Figure 1, showing the boom in lowered position.

Figure 3 is similar to Figure 2, but shows the boom in raised position.

2 Claims. 1 (01. 212-144) Referring now to the figures, we see that H is the main frame of a crane; Pivoted to the front thereof, and extending forwardly diagonally upward (Figure 3) is a boom I2. Also pivotally supported by the front of the main frame I I, and

extending forwardly diagonally upward at a steeper inclination, are tension members l3 which are supported by boom-hoist ropes [4 from the top of high A-frame IS on the main frame, and by fixed-length guys l6 extending from the top of the members l3 to the outer end of the boom. The A-frame I5 is of such height that members !3 are in tension for all positions of the boom (see Figures 2 and 3). Members 13 need not be separately pivoted to the frame. As shown,they are attached to the boom adjacent its foot.

Short suspender members I! support approximately the middle of the boom from guys l6, and are preferably of such length that there is an initial angle in the guys due to sag of the boom, so that the sag will be straightened out when the guys straighten under load, all as described in the above-mentioned patent to Davidson.

The guys need not be ropes; other sorts of tension members, capable of angular, or even non-angular, bending at the point of attachment of the suspender members, would suffice, although ropes are simpler, being easier to rig and adjust.

The importance of having the guys 16 be fixedlength should be stressed. For if these guys were merely reaches of the boom-hoist ropes l4, it would be nearly impossible to maintain a proper adjustment of their relative lengths.

The presence of tension members I3 facilitates a permanent adjustment of the proper relative lengths of guys It and suspenders IT.

The hoist rope 18 runs from a winch 19 on the main frame I I, over a sheave 20 on boom I2, thence over a sheave 2| at the outer end of the boom, and thence downwardly to the load (not shown) to be delivered thereby. Other fairlead means than sheave 20 could be employed, or such means could be omitted.

From the foregoing, we see that by substituting tension members and a high A-frame for the conventional mast and low A-frame, I have greatly reduced the weight of my front end while increasing the weight of the A-frame to a lesser extent thereby effecting a net decrease in weight and a backward relocation of the center of gravityof the whole machine, thereby reducing the moment of momentum, without losing the advantage of the fixed anchorage for the guys I6 and suspenders I l in all positions of the booml 3 Although I have show a two-legged boom, rather than a single-strut or other type of boom, it is clear that my invention is equally applicable to other types of boom and other types of suspenders therefor.

Having now described and illustrated one form of my invention, I wish it to be understood that my invention is not to be limited to the specific forms orarrangementsoi parts herein described and shown.

I claim:

1. In a suspension for a long slender upwardly inclined crane boom, the combination of 1 a mainframe; means thereon for pivotal support of the foot of the boom; first tension means, of fixed length, extending upwardly from a pivotal support by the main frame adjacent the foot of the boom; fixed-length guy means from theQupper,

end of the first tension means to the outerend of the boom; fixed-length boom-suspension means between an intermediatepoint on said guy means and-the boom; second tension means, of variable length, between an elevated point on the main frame and the upper end or" the first tension means, for supporting the first tension means;

the point of attachment of the second tension' REFERENCES CITED The following references are of record in the file of this patent;

' UNITED STATES PATENTS Number Name Date 1,628,972 Hansen May 17, 1927 2,187,714 Woodeson et a1. Jan. 16, 1940 2,378,915 Davidson June 26, 1945 2,382,767 Zeilman Aug. 14,1945 2,391,440 Anderson Dec. 25-, 1945' 2,392,760 Moody Jan. 8, 1946 2,411,305 Taylor et a1 No v.,19, 1946 

